Windshield Washer Fluid & Fire: A Chemistry Lesson
BY: MELINDA AMADOR | NOVEMBER 29th, 2021
It’s that time of year again – temperatures are dropping and our roads become slushy, slick, and icy. Did you know that in Canada windshield washer fluid for your vehicles can come in a variety of blends? Some blends are formulated to remove bug debris in the summer months and some are specially formulated for our very (very) cold winters. What is the secret ingredient for de-icing our windshields, and why is it the topic of a Fire Code discussion? It all comes down to chemistry and a property of certain flammable liquids – miscibility.
With a bit of chemistry knowledge and an understanding of our Fire Codes – the flammability of a very common Canadian commodity and how it’s regulated will be uncovered…
WHAT IS MISCIBILITY?
The term ‘miscible’ is defined in Merriam-Webster as “capable of being mixed; specifically, capable of mixing in any ratio without separation of two phases”. This means that two liquids can be mixed together to make a single, homogeneous solution with unique properties and characteristics from the original two liquids. In contrast – consider water and oil – typically, these two fluids don’t mix well at all and will separate into two phases if left to rest. After you’ve tried to mix water and oil – you’ll be left with water and oil, and their individual properties will not have changed.
The miscibility of certain flammable liquids with water (water miscible liquids) is important to understand when we consider the classification of different solutions and their performance under fire conditions.
Certain flammable liquids will mix readily with water to form a new solution – and the new mixture will present different flammability characteristics from the pure fuel. Typically, when we consider flammable liquids there are a few important indicators of fire risk, these include (but are not limited to): flash point, fire point, heat of combustion, and heat release rate. As more water is added to a water-miscible flammable liquid – the solution will start to behave more like water and less like a fuel. For example, at a certain concentration of water – the liquid will no longer have a fire point. This means that the liquid solution will not sustain a fire or cannot burn – as insufficient flammable vapours are released from the mixture. This is different from mixtures of gasoline and water, for example. As adding water to gasoline doesn’t necessarily change the flammability of gasoline – the two liquids will remain separate.
A few common liquids that are water miscible include: methanol, ethanol, isopropanol (IPA, 2-propanol), and acetone. These solvents are common in various industries and applications, and they are also regulated as flammable liquids under Part 4 of the National Fire Code of Canada (NFC). Of specific importance to this discussion is methanol – the common ingredient in our ‘antifreeze’ or de-icing windshield washer fluid.
HOW ARE WATER MISCIBLE LIQUIDS TREATED IN THE NFC?
Generally, the storage, handling, and use of flammable liquids is regulated by Part 4 of the NFC. These liquids are classified as described in Subsection 4.1.2., “Classification”, based on material flash point and boiling point. As defined in the NFC, a flammable liquid is “a liquid having a flash point below 37.8°C and having a vapour pressure not more than 275.8 kPa (absolute) at 37.8°C as determined by ASTM D 323, “Vapour Pressure of Petroleum Products (Reid Method)””. Pure methanol is generally accepted as having a flash point of 11°C [Fire Protection Guide to Hazardous Materials, 2010 Edition] and is classified as a Class IB flammable liquid.
In the absence of a solution-specific flash point determined by testing, it can be difficult to classify mixtures of liquids with accuracy. A conservative approach would be to consider that a mixture of liquids may present similar flammability characteristics to the most hazardous component. However, this approach can be overly cumbersome and may not reflect the true risk, especially when the solution involves water and methanol. There are literature resources that can be used to assist in classifying water-methanol mixtures, and generally when the concentration of methanol in water is not more than 20% by volume, the blends are not considered to present a fire hazard in the same way that a pure flammable liquid would. Under the current Code, an argument could be made that the liquid is not regulated as a flammable liquid under Part 4 – however, this may be subject to local jurisdiction approval and may require a detailed professional evaluation depending on the applications involving the solution. Where blends have concentrations of methanol in excess of 20%, the solution may be classified as a Class II, Class IC, or Class IB liquids under the NFC – depending on the specific solution ratios of water and methanol, and based on the solution flash point.
For the purpose of this discussion, it’s worth noting that a 50% mixture of methanol and water is exempt from compliance with NFC Section 4.2, per Clause 4.2.1.1.(2)(b); however, the exemption only applies to 5 L, closed-containers. This will exempt your personal container of windshield washer fluid that you purchase at a local retail outlet – but it doesn’t inform the overall treatment of water-miscible flammable liquids once in a production or large-scale use application (e.g. industrial applications). Under these circumstances, a professional assessment and classification of processing liquids may be required to apply the NFC requirements appropriately to the specific industrial application.
When we look beyond liquid classification and exemptions for small container handling and storage – the water-miscible nature of certain flammable liquids is also recognized under the NFC when we consider certain spill control measures and certain liquids. Specifically, NFC Sentence 4.1.6.1.(3) permits liquid spills and firefighting water to be directed to a sewer system, where the liquids are water-miscible (with restriction). This allowance recognizes that when water is applied to these liquids – via sprinkler or hoses – the liquid will behave less like a fuel and more like water.
It is also noted that ethanol, a Class IB flammable liquid, is treated entirely differently from other flammable liquids when it is present in water mixtures for consumer consumption – as it is defined as a ‘distilled beverage alcohol’. While not exactly the same, ethanol and methanol do have similar water-miscible properties. This is an interesting distinction, and I’ll leave it to you to consider the reasoning – please share your comments below!
HOW IS WINDSHIELD WASHER FLUID TREATED ACROSS CANADA?
It’s not necessarily consistent – as the concentration of methanol can vary depending on local weather conditions and the storage of bulk, concentrated methanol solutions has become more common in different jurisdictions. For example, in the past, Alberta Municipal Affairs issued a Fire Code Safety Alert for the storage of windshield washer fluid – requiring a Class IC classification and affecting many automotive repair/sales facilities which may not have considered the flammability hazards of windshield washer fluid. The classification is likely tied to the most common blends, and not on a concentrated or high-methanol percentage based solution.
It may be of interest to know that a proposed change to the NFC was submitted and included in the 2019 Public Review cycle. This proposed change was presented to include composition thresholds for certain flammable liquids in water solutions and associated Part 4 classifications – effectively mapping the liquid classification based on the composition of the mixture. The adoption of this proposed change would provide a link between the chemical properties associated with these types of liquids and the application of the NFC – to improve national consistency and to reduce the burden on practitioners and owners/operators to classify water-miscible liquids.
Was this helpful? Have you encountered classification challenges with water-miscible liquids? Please share your experiences below!